Conduits are normally incorporated in a construction element that divides, for instance, two compartments. Such a construction element may also be referred to as a partition. A pipe may extend through the conduit from one of the two compartments into the other. These conduits are often referred to as pipe penetrations or transit systems. Such a conduit is often present in constructions formed on the basis of civil engineering. Factories, buildings, drainage systems, tunnels, subways, etc. all comprise such penetrations. However, also constructions formed on the basis of nautical engineering do comprise such conduits. One finds them on board of vessels and/on other offshore applications such as oil rigs.
These penetrations are seen as unwelcome necessities in such a construction. Pipes for, for instance, water distribution and water wastage systems, air-conditioning systems, hydraulic and pneumatic control, sprinklers etc but also for transport of gas, or oil, need to be extending throughout such a construction, even though this entails introducing weak spots in a separation of the compartments.
Such weak spots do not manifest themselves to a great extent in the mechanical strength of the construction but much more in the possibility of undesired transport of physical phenomena throughout the structure.
An example is a fire which itself needs to be confined, as long as possible, to only one area. This is important not only to allow for control and extinguishing the fire, but also to provide time for people present in compartments near to the fire for reaching a safe distance from the fire before it further expands. To prevent smoke and/or fire from passing through the conduit from one compartment to another, the conduit is usually provided with a material that closes the conduit, at least for some time, when the conduit is exposed to heat due to a nearby fire.
Another form of transport that needs to be prevented is the supply of air to a fire which takes place in a compartment. Particularly for on-shore constructions, it is believed that fire is fed with oxygen as supplied through burned-out conduits and that it spreads itself throughout a multi-storey building, if transport of air can freely occur between different levels of compartments. It is also for this reason desirable that a conduit is closed off, when on one side of the conduit a fire takes place.
Although above reference is made to a construction element having a conduit and dividing two compartments, it is also possible that a construction element separates a compartment from the surrounding environment. It is thus possible that one side of the construction element is exposed to atmospheric conditions.
It will be appreciated that a pipe extending through a conduit, the conduit itself and the construction element into which the conduit is incorporated, may each be made of a material that allows for the conduction of heat. The efficiency for conducting heat depends on the type of material and the dimensions of that material. In principle, heat can in such a situation be supplied to the inner space of the conduit via at least two different routes. The first route is via the pipe extending through the conduit and the second route to the inner space of the conduit is via the material out of which the conduit itself is made. As in offshore constructions and vessels, conduits are usually made of metal, i.e. a good heat-conducting material, heat is usually rapidly supplied to the inner space of the conduit via the second route. Of course, heat may also exclusively be applied to the inner space of the conduit via the first route, in a situation where the partition is for instance a concrete wall and the conduit is formed by a through-hole in that wall.
There is a strong tendency in both the offshore and the on-shore construction industry to make pipes, in particular pipes of so-called service systems as referred to above, of a plastic material such as for instance PVC, PP-R, ABS and HOPE. Relative to aluminium or metal pipes, such plastic pipes offer an enormous reduction in weight, clearly advantageous in shipbuilding. As known, plastics are not susceptible and do not contribute to corrosion, advantageous in both the offshore and on-shore construction industry. Such plastic pipes are observed to suffer much less from sedimentation in the pipes, particularly when compared to steel pipes, giving plastic pipes advantages in waste water installations. On exposure to heat, however, such plastic pipes may weaken, i.e. become soft, and are therefore further in this specification referred to, as made of a thermally weakenable or a thermally softenable material, or in short as thermally weakenable pipes. The phrase thermally weakenable material refers thus in general to materials comprising or consisting of plastic. However, it is envisagable that also pipes made of or made with fibreglass form thermally weakenable material and these are therefore equally embraced by the term thermally weakenable pipes.
It will be clear that such weakening of the pipe will occur more rapidly in a conduit which is made of metal and incorporated in a metal construction element or partition. The conduit will then act as a kind of oven surrounding the pipe of the weakenable material, leading to local collapse of the pipe. However, a heated inner wall of a through-hole in a stone or concrete wall which is exposed to a fire, may equally act like an oven, even though the heating-rate will in that case be different than the heating-rate for “the metal oven”. A stone or concrete wall will absorb much more heat and is a poor conductor of heat. The second route for the supply of heat into the conduit is in that case therefore much less effective. In such a situation it may well be that the first route, i.e. transport of heat into the conduit via the pipe itself, is by far the most dominant route if not effectively the only one.
It is common practice to seal the space between a conduit and a pipe as extending through the conduit, with a sealing system. Such a sealing system may provide sealing capacities before exposure to heat, and may for instance seal such that gas and/or water cannot penetrate through the annular space between the pipe and the conduit.
In particular for conduits through which a single pipe of a thermally weakenable material extends, advanced sealing systems have been developed. Reference is made to EP 120 075.9 31of the same inventor, describing so-called “crusher plugs”. At each end of the conduit is a plug inserted in the annular space between the conduit and the pipe extending to the conduit. The crusher plug is made of a thermally expandable material. Upon exposure to heat, the crusher plug expands. However, as the conduit is of a very rigid material, expansion is only possible radially inwards. As upon the exposure to heat the thermally weakenable pipe has started weakening, the radial inward expansion of the plug crushes the pipe further and therewith closes the pipe off, as well as the complete conduit. The use of such plugs is very advantageous for conduits through which a single pipe extends, as the annular space which needs to be shut off by the plug is very well defined.
WO 2006/097290, also of the present inventor, discloses a conduit through which a plurality of pipes extend. For sealing that conduit a system is described that comprises a multitude of heat expandable rubbery sleeves. The sleeve material is made heat expandable by incorporation of heat expandable graphite into the rubbery material. Such a sleeve is also referred to as a filler sleeve. Usually, the sleeve is easily bendable, soft, and has relatively poor mechanical properties. This makes the sleeves perfect for inserting in a conduit and therewith filling the conduit. The sleeves are applied in a fashion parallel to each other and parallel to the pipe. The system further comprises a fire-resistant and/or watertight sealant. The sealant is applied against the ends of the sleeves and forms a sealing layer that seals off the conduit.
A system as described in WO 2006/097290 is usually applied in a conduit which is very large in cross-section relative to the cross-section of the pipe extending through the conduit. The main reason for this is that there has to be enough space in the conduit for filling the conduit with the heat expandable rubber sleeves, so that these heat expandable sleeves are during expansion in radial (transverse) direction capable of closing the conduit fully off. As there is space between the filler sleeves as well as in each empty sleeve, thermal expansion can freely occur in the radial (transverse) direction as soon as the temperature in the conduit reaches a point from where the thermally expandable rubber material will expand.
Although there is in axial (longitudinal) direction per unit of length between the sealant layers, no space for expansion available, and the expansion is expected to be larger in axial direction than in radial direction given the amount of heat expandable material that is axially aligned, the expansion of the filler sleeves is initially still predominantly radially oriented.
Without wishing to be bound by any theory this is thought to be a result of three factors. Firstly, as soon as thermal expansion occurs, even though at low temperatures and therefore still only to a limited extent, the axially expanding sleeves feel constrained between the sealant layers and start buckling, therewith removing pressure on the inner wall of the sealant layers. Secondly, the expansion will find its way radially given the little resistance the expansion experiences on radially expanding. (Remember, space is available radially, not only due to the space in and between the sleeves, but at higher temperatures also due to the weakening pipe within the conduit). Thirdly, air originally trapped in the conduit and reaching a high pressure due to the raised temperature and volume reduction in the conduit, will at some stage find its way out presumably through small cracks which have become available in the sealant layer without a breaking up of the sealant layer. This escaping of air offers “new volume” made available in the conduit, into which the expanding sleeve layers can expand into, whilst staying within the confinement of the conduit and the sealant layers.
At some stage, the expanding forces in the conduit as restrained by the sealant layers become so high that the sealant layer breaks.
This breaking is then in itself not a problem as the expanded sleeves have sealed off the conduit before the sealant layer breaks.
Currently there is a strong desire to have smaller and shorter conduits, in order to save both weight and space, without compromising sealing capacity both before and during exposure to a fire.
Conduits which are smaller in cross-sectional dimensions do have little capacity for letting the onset of expansion of the filler sleeve material to predominantly take place in radial direction. In such conduits, it is the radial expansion which is constrained. Hence, the expansion will at a much earlier stage attempt to find its way axially, resulting in early breaking of the sealant layer, with a possibility that the sealant layer breaks before the conduit has been fully closed off by the expanding material. In such a situation it is needed to apply instead of a sealant layer a much stronger “structure”. In response thereto one applies in practice a plug designed to sustain high pressures rather than a sealant layer. It turns out that a conduit with expandable filler sleeve in the annular gap between the conduit and the pipe extending therethrough, on both ends of the conduit closed off by a deeply inserted plug, effectively allows the filler sleeves to expand radially and close the conduit and pipe fully off.
However, the drive for further reduction of the cross-sectioned area of the conduit relative to the pipe, continues in attempts to save even more space and even more weight.
When the annular gap between the conduit and the pipe becomes very small, a plug cannot be inserted and can thus not offer resistance against axial expansion of the tiller sleeve material. The situation becomes even worse when the pipe is slightly off-centre relative to the conduit.
On the market is a system available that comprises two steel collar-shaped casings filled with relatively thin, usually wrappable sheets of rubbery heat expandable material. Each of these casings is mountable in front of the conduit around the pipe and against the partition to provide resistance against axial expansion of the heat expandable material and to force the expansion to direct itself radially inward so as to close the pipe (and ideally also the conduit) fully off upon exposure to heat. Such a system has many drawbacks. First, it requires two extra mounting steps (one casing on each side of the partition) and facilities for mounting at parts of the partition “surrounding” the conduit. Secondly, the space saved in cross-sectional direction is to some extent lost due to the need to mount these to the parts of the partition surrounding the conduit. Thirdly, the casings itself require space, so that in axial direction the conduit or the penetration effectively has become longer instead of shorter.
It is an object of the invention to provide a thermally expandable fire-stop system for application in combination with a rigid and thermally stable conduit having an inner wall defining an inner space through which a pipe, being a, relatively, weakenable pipe, extends, or will extend.
It is an object of the invention to provide a rigid and thermally stable conduit having an inner wall through which a pipe, being a, relatively, thermally weakenable pipe having an outer wall, extends, or will extend, such that it includes a thermally expandable fire-stop system in an economically attractive way.
It is an object of the invention to provide a method for providing a fire-stop system in a rigid and thermally stable conduit having an inner wall defining an inner space through which a pipe, being a, relatively, thermally weakenable pipe, extends or will extend.